pthread_condattr_getpshared(3T)

NAME

pthread_condattr_getpshared(), pthread_condattr_setpshared() — get or set the process-shared attribute

SYNOPSIS

#include <pthread.h>

int pthread_condattr_getpshared( 
   const pthread_condattr_t *__restrict attr, 
   int *__restrict pshared 
); 

int pthread_condattr_setpshared( 
   pthread_condattr_t *attr, 
   int pshared 
); 

PARAMETERS

attr: Pointer to the condition variable attributes object whose process-shared attribute is to be set/retrieved.
pshared: This parameter either specifies the new value of the process-shared attribute (set function) or it points to the memory location where the process-shared attribute of attr is to be returned (get function).

DESCRIPTION

The attributes object attr must have been previously initialized with the function pthread_condattr_init() before these functions are called.

The functions are used to set and retrieve the process-shared attribute in a condition variable attributes object. The legal values for the process-shared attribute are:

PTHREAD_PROCESS_SHARED: This option permits a condition variable to be operated upon by any thread that has access to the memory where the condition variable is allocated. The application is responsible for allocating the condition variable in memory that multiple processes can access.
PTHREAD_PROCESS_PRIVATE: The condition variable can be operated on only by threads created within the same process as the thread that initialized the condition variable. If threads of differing processes attempt to operate on such condition variable, the behavior is undefined.

The default value of process-shared is PTHREAD_PROCESS_PRIVATE.

pthread_condattr_setpshared() sets the process-shared attribute in attr. The new value of the process-shared attribute of attr is set to the value specified in the pshared parameter.

pthread_condattr_getpshared() retrieves the value of the process-shared attribute from attr. The value of the process-shared attribute of attr is returned in the pshared parameter.

RETURN VALUE

Upon successful completion, pthread_condattr_getpshared() and pthread_condattr_setpshared() return zero. Otherwise, an error number is returned to indicate the error (the errno variable is not set).

ERRORS

If any of the following occur, the pthread_condattr_getpshared() and pthread_condattr_setpshared() functions return the corresponding error number:

ENOSYS: _POSIX_THREAD_PROCESS_SHARED is not defined and these functions are not supported.

For each of the following conditions, if the condition is detected, the pthread_condattr_setpshared() function returns the corresponding error number:

EINVAL: attr is not a valid condition variable attributes object.
EINVAL: The value specified by pshared is not a legal value.

For each of the following conditions, if the condition is detected, the pthread_condattr_getpshared() function returns the corresponding error number:

EINVAL: The value specified by attr or pshared is invalid.

WARNINGS

If a condition variable is created with the process-shared attribute defined as PTHREAD_PROCESS_SHARED, the cooperating processes should have access to the memory in which the condition variable is allocated.

AUTHOR

pthread_condattr_setpshared() and pthread_condattr_getpshared() were derived from the IEEE POSIX P1003.1c standard.

STANDARDS CONFORMANCE

pthread_condattr_setpshared(): POSIX 1003.1c.
pthread_condattr_getpshared(): POSIX 1003.1c.